Heat-resisting articles of alloy steel



Patented May 27, 1924.

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PERCY A. E. .ARMSTRONG, OF LOUDONVILLE, NEW YORK, ASSIGNOR TO LUDLUM STEEL COMPANY, OF WATERVLIET, NEW YORK, A CORPORATION OF NEW JERSEY.

HEAT-RESISTING ARTICLES F ALLOY STEEL.

No Drawing.

To all whom it may concern:

Be it known that I, PERCY A. E. ARM- STRONG, a subject of the King of Great Britain, and residing at Loudonville, county of 5 Albany, and State of New York, have invented a certain new andv useful Improvement in Heat-Resisting Articles of Alloy Steel, of which the following is a specification.

The present invention relates to articles in which the quality of non-scaling when heated is of importance. Good examples of such articles are valves for internal combustion engines, drawn electrical resistance heating elements and electrical heating elements in the form of cast grids to be run at temperatures not substantially in excess of red heat, and various other uses, such as furnace bars, automatic Stoker parts, carburizing boxes, annealing boxes, lead pots and other uses Where resistance to hot oxidation is important.

The heat resisting articles of the present invention are made of'alloy steel containing silicon as the predominent alloying element.

Other metallic elements may be used in addition to silicon, preferably chromium, but instead of chromium or in addition thereto, other metals such as tungsten, molybdenum, cobalt,- nickel, zirconium, vanadium, uranium, titanium, and other high melting point metallic elements may be used.

The silicon content is preferably not less than about 1.5%. With this amount or more of silicon the resistance to formation of porous or loose scale when heated becomes quite noticeable, and is particularly noticeable above 3% and up to about 6% of silicon. With silicon above 6% the alloy becomes too brittle for practical uses. silicon content is about 3.75% with which the alloy is readily workable and has good heat resisting qualities, but there may be considerable variation from this within the The preferable extreme range of silicon, as from 34% sili-' Anplication filed April 22, 1922. Serial No. 556,078.

' tent should be above 5% and preferably above The maximum chromium of the present alloy is 3%, chromium above 3% bemg claimed in my Patent No. 1,322,511 of Nov. 25, 1919.

The approximate specific resistance of the alloy with varying silicon content is from about 45 microhms per 0. c. for 1.5% silicon up to about 95 microhmsper c. c. for 6% of silicon. As the chromium percentage is increased in this alloy an increasing ohmic resistance is obtained, but the high resistance is largely a function of silicon content. The resistance to production of loose, porous destructive scale upon heating is likewise increased with increase of silicon content.. v

Itor example, with carbon .30, chromium 3%, silicon 2.5%, the alloy is very resistant to con 3.75%, the alloy is resistant to scaling when heated to temperatures for long periods, of approximately 1600 F.;

With carbon 20%; chromium 1%, silicon 5%, the alloy is very scale-resistant when heated to temperatures for long periods up to approximately 1650 F.-; and

Vith carbon 25%, chromium 1.25%, silicon 6%, the alloy is very resistant to scalin when heated u to approximately 17 00 for long perio s.

Articles made of the alloy have very excellent Wear-resistance to mechanical abrasion, such as occurs in the valve guides of an automobile engine, and even with carbon as low as .20%.30%, the steel can be hardened to a material extent when quenched from a temperature sufficiently high above its transformation point and when about 3% of chromium is present in the alloy it plan be hardened so that it is practically file ard.

This alloy is readily rolled and forged, particularly if the silicon is kept under 5%, and even with silicon as high as 6%, it can be worked if reasonable care is taken. Chromium adds to the physical properties and aids in keeping the grain size small. For

this reason, chromium in the neighborhood of 3% is preferably used. llhe approximate range of composition is as follows: silicon 1.5% to 6%, carbon .05% to 1%, chromium or alternative metallic elements or mixture other ways.

I claim:

1. Articles having high resistance to hot oxidation and composed of alloy steel containing silicon 1.5G%, carbon .O51%, chromium between 1% and 3%, and. the principal part of the remainder iron.

2. Articles having high resistance to hot oxidation and composed of alloy steel containing silicon 1.56%, carbon .20.40%, chromium between 1% and 3%, and the principal part of the remainder iron.

3. Articles having high resistanceto hot oxidation and composed of alloy steel con-v taining silicon 25%, carbon .15.50%,

chromium between 1% and 3%, and the principal part of the remainder iron.

4:. Articles having high resistance to hot oxidation and composed of alloy steel containing silicon 3.75%, carbon 30-50%, chromium 1.5%, and the principal part of the remainder iron.

5. Articles having high resistance to hot oxidation and composed of alloy steel containing silicon 3-1%, carbon .15.50%, chromium between 1.5% and 3%, and the principal part of the remainder iron.

6. Articles having high resistance to hot oxidation and composed of alloy steel containing silicon 3 1%, carbon .15 .50%, chromium between 1.5% and 3%, manganese under 1.5%, and the principal part of the remainder iron.

7. Articles having high resistance to hot oxidation composed of ferrous alloy having silicon 1.56%, carbon between as loW as practical and 1%, chromium between 1% and 3%, manganese under 1.5%, and the principal part of the remainder iron.

In testimony that I claim the foregoing it hereto set my hand, this 19th day of April,

PERCY A. E. ARMSTRONG. 

